1. Field of the Invention
This invention relates to a semiconductor device and to the manufacturing method thereof, and in particular, to a semiconductor device having a low dielectric constant film as an interlayer insulating film and to the manufacturing method thereof.
2. Description of the Related Art
In order to minimize any delay of wiring portions in a semiconductor device, it is highly desirable to minimize the relative dielectric constant of an interlayer insulating film. In order to secure a sufficiently low relative dielectric constant, it is possible to employ a method wherein the interlayer insulating film is made into a porous insulating film by incorporating voids or pores into the interlayer insulating film. In this regard, it is possible, in the case of an organic silicone film to reduce the relative dielectric constant of the film to 2.5 or less if the average diameter of the pores is within the range of about 2 to 3 nm.
The larger the diameter of pores is, the lower the relative dielectric constant of the insulating film would become. However, even if it is possible to lower the relative dielectric constant of insulating film in this manner, the reliability of wirings may be badly affected by this. For example, in the case of a porous insulating film whose maximum pore diameter is 4 nm or more, the following inconveniences would be brought about on the occasion of forming a metal wiring by a damascene method. Namely, if such an insulating film is worked to form a trench therein, pores of relatively large size are exposed from the sidewall of the trench, thus producing hollows thereon. As a result, it becomes difficult to form a continuous barrier metal film thereon. As a result, the reliability of wirings may be badly deteriorated.
On the other hand, if the average diameter of pores in the porous insulating film is to 1 nm or less, it may become difficult to sufficiently minimize the relative dielectric constant of interlayer insulating film.